1. Technical Field
This invention relates to a mobile communications terminal for use in a cellular communications system, comprising an electronic circuit for receiving a wire-less communication signal carrying signal channels having processing means for extracting the signal channels.
2. History of Related Art
A typical cellular telecommunications system cell is organized about a base-station equipped with multiplexing means for transmitting communication signals carrying signal channels from a wired telephone net onto a frequency carrier that is broadcast by an antenna system over an area that the cell is designate to cover. A set of individual mobile subscriber stations—i.e. a mobile communications terminal—are each equipped to receive the broadcast frequency carrier and to de-multiplex the specific channel the terminal is intended to receive. Typically, two-way communication is supported and the mobile communications terminal is adapted to transmit signals to the base-station for subsequent multiplexing and distribution to a wired net or another base-station.
In such a wire-less communications system, an assigned radio frequency bandwidth of frequencies is simultaneously shared by multiple subscribers using various multiple access techniques e.g. code division multiple access (CDMA). In CDMA systems multiple subscribers can be accommodated on a single carrier in which each subscriber is assigned one or multiple codes that is used to carry information. A code waveform taken from a set of orthogonal waveforms allows the system to transmit information in separate information channels. These separate information channels can be used to carry individual information to different users and/or enable multiple information streams to one user.
However, in such systems different types of interference may occur and diminish the communication quality. The interference situation can vary from time to time depending on the location of the mobile communications terminal relative to the base-station, the location of other base-stations, the actual load of the system, and the type of traffic on the communication channels. Furthermore, moving the mobile communications terminal relative to the base-station and movement of other objects affecting the transmission path between the base-station and the mobile communications terminal can affect the interference situation.
Basically, interference can be divided into two groups:                1. inter-cell interference, and        2. intra-cell interference.        
Inter-cell interference originates from one or more neighbouring base stations. The fading of inter-cell interference is uncorrelated with the fading of the communication signal. In the following, inter-cell interference refers to interference that has an uncorrelated fading or no fading. Thus, inter-cell interference can be caused by thermal noise etc.
Intra-cell interference originates from the same base station as the base station communicating with the mobile communications terminal. Intra-cell interference is due to reception of non-orthogonal signals transmitted from the base station (e.g. the synchronisation channel in WCDMA) or due to multi-path propagation of the communication signal). One important feature of intra-cell interference is that it travels the same path as the communication signal and thus experience the same fading.
The type of interference that a communication signal is distorted with at reception by a mobile communication terminal is an important parameter for optimisation of several algorithms in the terminal and in turn for improving the quality of the wire-less communication.
There exists known methods for classifying interference by means of spectrum estimation techniques. However, these methods are very complex and involves large processing means. The different types of interference may degrade performance of a mobile communications terminal. Thus there is a need for a less complex method that can be implemented in small-sized and/or mobile communication terminals.
Therefore, the prior art involves the problem that a present type of interference affecting performance in the form of transmission capacity and/or quality of a mobile communications terminal is not determined—thereby not making it possible to take the type of interference into communications terminal.